Portable fork lift truck



United States Patent PORTABLE FORK LIFT TRUCK Lester W. Leavitt,Jacksonville, Fla.

Application October 2, 1956, Serial No. 613,471 2 Claims. (Cl. 187-11)This invention pertains to portable fork lift trucks.

A general object of the invention is to provide an improved portablefork lift truck, and more particularly, to provide an easily movablefork lift truck wherein the fork lift carriage is power operated;wherein the carriage will remain in its then position upon the operatorremoving his hand from the controls; wherein the operator uses only onehand to operate and brake the lift; and wherein manual operation of theoperating brake is necessary only to release such brake during thelowering operation.

While power operated fork lifts comprising a movable carriage operatingbetween a pair of vertical uprights have been heretofore suggested, suchprior fork lifts have been generally expensive to construct and havecontained intricate lifting mechanisms and separate braking devicesrequiring the operator to manipulate several unrelated controlspractically simultaneously. In practice such lifts have been diflicultto operate quickly and safely, and have usually required extensivemaintenance, adjustment and servicing to maintain their continuedoperability.

Further objects of this invention accordingly are to provide a compactportable fork lift truck of simple,

gged and inexpensive construction which requires a of skill for quick,safe, one hand operation and a minimum of adjustments to maintain thedevice in eflicient working condition. Another object of the inventionis to provide a stable portable fork lift truck having a small,inexpensive, self-contained power unit which is arranged to furnishrelatively great lifting power to a movable lifting carriage. A stillfurther object of the invention is to provide, in a portable fork lifttruck, an improved anti-roll floor brake of simple construction whichrequires no adjustment and is quickly and easily operable.

The novel features which are believed to be characteristic of thisinvention are set forth with particularity in the appended claims. Theinvention itself, however, both as to its organization and method ofoperation, together with further objects and advantages thereof, maybest be understood by reference to the following description taken inconnection with the accompanying drawing, in which:

Fig. 1 is a perspective view of a portable fork lift truck embodying theinvention;

Fig. 2 is a perspective view of a portion of the truck showing thecarriage in an upper position;

Fig. 3 is an enlarged rear view of a portion of the truck showingdetails of the brake drum, winding reel assembly and the brake band;

Fig. 4 is a sectional view taken along the line 4-4 of Fig. 3; and

Fig. 5 is a rear view on an intermediate scale of a lower portion of thetruck showing details of the springloaded anti-roll block floor brakeand operating means therefor.

Referring now to the drawing, Fig. 1 shows a portable fork lift truck 1having a movable carriage 50 located in an intermediate position on avertical frame 2. As seen, the lift truck comprises, in combination, avertical frame generally referred to as 2, the frame comprising twooppositely disposed channel bars 3 and 3 spaced in parallel relation.The channel bars have outwardly extending rear flanges 4 and 5respectively, and like front or forward flanges 6 (see Fig. 2) and 7respectively which define the outwardly facing channels of the bars. Anupper cross member 8 terminally joins the channel bars which are furtherinterconnected by intermediate cross members 9 and 10, which liesubstantially in the plane of the front flanges, and by cross member 11,which lies substantially in the plane of the rear flanges. The framealso includes upstanding rear braces: 12 and 13, afi'ixed respectivelyto the rear flanges of the channel bars, and with the frame, rigidlymounted on a horizontal base 14.

The base 14 includes two oppositely disposed horizontal legs 15 and 16projecting forwardly from a base plate 17, to which they are joined.Legs 15 and 16 are connected by a front angle bar 18. Base plate 17preferably has a greater length than the width of the frame and isprovided with a pair of caster wheels 19 and 20 which are preferably thesame size as but spaced further apart than wheels 21 and 22 supportingeach of the forward legs.

The power means for operating the lift mechanism is mounted on base 14and cross member 11, and comprises an electric drive motor 23, mountedon cross member 11 to extend rearwardly therefrom. Drive shaft 24 (seeFig. 3) of the motor extends forwardly through cross member 11. Themotor 23 is energized by a storage battery 25 mounted on base 14 betweenchannel bars 3 and 3.

Motor operating control elements "are provided including a push buttonswitch 26 attached to the frame preferably in a position convenientlyproximate to operating brake release handle 40, a limit switch 27disposed on channel bar 3' in position to be engaged and operated bycarriage plate 51 near the desired upper limit of the fork lift travel,and a motor control solenoid operated relay 84. Switch 26, which isspring biased into normally open position and which is manuallycontrolled to closed position by thumb pressure, is connected in seriescircuit with relay 84 and with normally closed limit switch 27, thecircuit being connected to battery 25 and operable, in response toclosure of push button switch 26, to close relay 84, thereby to completethe power circuit between battery 25 and motor 23 through power cableand ground, the ground circuit being established by the metal frame.

The motor is belt connected with the brake drum assembly 29, the motorbeing so connected with the battery that, when energized, the brake drumassembly rotates in a reel winding direction, as is more fully discussedand shown with reference to Figs. 3 and 4 herein.

Referring now to Figs. 3 and 4, in which the reference numerals indicatethe same parts referred to in Fig. l, the drive shaft 24 mounting thedrive pulley 28, shown in broken lines on Fig. 3, is connected withbrake drum assembly 29 by drive belt 30, which couples pulley 28 with apulley portion 30 of the drum assembly. Cable reel 31 comprises anintegral portion of drum assembly 29 and rotates with drum 34 and pulleyportion 30'. It will be understood that the motor is so connected withthe assembly that, when energized, drive belt 36 rotates brake drumassembly 29 in a reel winding and carriage lifting direction, which willbe counterclockwise as viewed in Fig. 3.

The braking function is provided by generally circular brake band 32,having a brake lining 35 attached thereto and being engageable withbrake drum 34, and having a stationary end 33 of the band anchored tocross member ll). End 33 encircles a post or bolt 58 and pivots slightlythereon, post 58 being aflixed to cross member 10. The brake bandsubstantially encircles the brake drum and has at its other end 36 aplate 59 aflixed thereto and having a plurality of openings 64 to retainend 38 of a tension spring 37 and to permit adjustment of the springtension. Tension spring 37 is attached at its other end .39 to the frameand functions to urge end 36 of the brake band in a direction to tightenthe band about the brake drum. An operating brake release handle 40pivotally attached to end 36 of the brake band is provided for manuallyloosening the brake band on the brake drum. As shown, handle 4 receivesa manual hand grip 41 on the rearward or hand engageable end 55 thereofand is pivotally attached at its forward end 42 to cross member Bill bya pivot bolt 56.

As best seen in Fig. 4, brake drum assembly 29 receives and is rotatablymounted on spindle 43. The spindle 43 is rigidly mounted rearwardly oncross member 10, such as by bolts 36, and projects rearwardly therefrom.

Referring now to Fig. l and Fig. 2, in the latter of which the referencenumerals indicate the same parts referred to in Fig. l, a flexibleelement such as steel cable 44 is wound on reel 31 and extends upwardlytherefrom over free running back idler pulley 45 and front idler pulley4 5, both of said idler pulleys being mounted on upper cross member Thecable then extends downwardly from idler pulley 46 and passes aroundcarriage pulley 4-7 which is mounted rearwardly on carriage yoke 48. Thecable extends upwardly from the carriage pulley and passes overstationary free running upper pulley 49, which may be somewhat largerthan the idler and carriage pulleys, and is mounted forwardly on crossmember 9. The cable end 4 is fixed to carriage yoke 48. It will be seenthat the cable is so wound on reel 31 and threaded on the pulleys andaflixed to carriage yoke 48 that, when the brake drum assembly isrotated by the motor in a reel winding direction, the cable winds onreel 31, thereby imparting a lifting action to the carriage.

The movable fork lift carriage, generally referred to at 59, comprisesthe yoke 48 spanning the channel bars of flame 2, yoke 43 having rigidlyattached thereto two rearwardly projecting yoke plates 51 and 52. Anupper pair of rollers 53 and a lower pair of rollers 54 are so affixedinwardly on plate 51 that the rear rollers of each pair engage and rollupon the inner face 7 of front flange 7 of channel bar 3. The forwardrollers of each pair are positioned on plate Sl to engage and roll uponthe outer face 7" (see Fig. 2) of front flange 7. The construction isduplicated in the roller arrangement of yoke plate 52 permitting thisplate to travel along channel bar 3, as revealed by the broken awayportion shown in Fig. 2. Pork lift carriage 50 further comprises twoL-shaped forks 66 and 61 rigidly mounted on yoke 48 and extendingforwardly therefrom in spaced parellel relation, the forward ends 62 and63 respectively thereof being blunted to avoid injuring the objects tobe lifted.

As best seen in Fig. the anti-roll block brake 65 comprises an anti-rollblock 66 secured to rods 67 and 63 of yoke 69. The rods are slideablyenclosed respectively in tubes 70 and 71, which are rigidly attached toa crossmember 72 of the frame. The lower ends of the tubes such as end84 of tube 7t) have flanges such as 73 which serve as stops forcompression springs 75 and 76 respectively. The springs surround yokerods 67 and 6% and are compressed between block 66 and flanges 73 and74. A manually operated floor brake handle 77 is provided which has ahand engageable grip 78 and is pivotally connected to a tubular framecrossmember 79 at point 86. Handle 77 is connected between its ends bymeans of a link 31 to the midpoint of yoke 69. A hook shaped catch 82 ismounted on frame brace 13 and is engageable by handle 77 when theanti-roll block is disengaged from the floor.

A U-shaped tubular handle 83 is provided intermediate the frameconnecting channel bars 3 and 3' and protruding horizontally rearwardstherefrom. The handle serves as a grip means for guiding the truck alongthe floor, as a bumper to protect motor 23 and as a guard for handle 4t)preventing external objects from striking the handle and accidentallyreleasing the brake.

The operation of the invention is best understood by the followingdescriptive cycle of the lifting and lowering of a hypothetical boxconventionally resting on attached skids at approximately the level ofthe base of the truck.

The portable fork lift truck is manually rolled into position, usinghandle 83, with respect to the box to dispose forks 69 and 671 ofcarriage 5t) sufliciently beneath the box to support it in a stablemanner. The motor is operated by push button switch 26 to raise the boxwith the attached skids to be thus supported solely by the forks. Nowthe truck may be pushed or pulled by handle 83, pivoting on its rearcaster wheels 19 and 20, thus to be propelled to any desired position,such as facing the location in which the box is to be lifted andunloaded.

The operator may next raise the box by depressing the normally openoperating switch 26, the motor being so connected with the rotatablebrake drum assembly 29 that its driving force rotates the assembly in areel winding or carriage lifting direction. By the rotation of theassembly in such direction, brake drum 34 exerts an unwinding forceagainst its encircling brake lined band 32. It will be noted that band32 is attached at end 36 to tension spring 37 thus permitting the bandto be loosened from around the drum by this unwinding force and allowingthe assembly to rotate freely. This rotation of the assembly, of course,winds the cable 44 on reel 31 thereby elevating fork lift carriage 50 towhich the cable is attached.

The upward movement of the load-bearing carriage may be halted at anypoint, prior to engagement of the carriage with limit switch 27, byreleasing the operating switch 26 to permit it to reopen, therebybreaking the circuit and stopping the electric motor.

When the motor is de-energized, the weight of the forks and any loadthereon tends to urge the brake drum to rotate in a fork loweringdirection. This tendency, together with the tension of spring 37, causesband 32 frictionally to wrap tightly around the drum and elfectivelyprevent any appreciable unreeling of cable 44 from reel 31, unless anduntil the braking force is reduced by manual operation of brake releasehandle 4%. If by any chance, because, for example, of the wearing out ofthe brake band, or because some grease may have been inadvertentlyspilled on the drum, the brake hand does not operate automatically toprevent unreeling rotation of the brake drum, brake release handle 40may be pulled in the direction to additionally tighten the band aboutthe drum. [f it is found that manual tightening of the band by means ofhandle 40 in this manner is frequently necessary, it may be appropriateto increase the tension of spring 37 by engaging it with a different oneof openings 64.

If the operator for any reason fails to stop the lifting action beforethe maximum upper limit of carriage travel, carriage yoke plate Sll willengage normally closed limit switch 27 at the upper limit position ofthe carriage on the frame, the circuit will be broken, and the electricmotor stopped, preventing damage to the truck. Immediately, of course,the braking action of the band and the drum produce the safe effectivebraking action as hereinabove described.

If the operator desires to lower the carriage, either loaded orunloaded, he need only urge the operating brake handle 40 in a bandloosening direction and maintain the handle in such position, allowingthe carriage to gravitate. The carriage may be interrupted in itsdescent at any point by the operator releasing handle 40 which willpermit tension spring 37 to urge brake band 32 into contact with thedrum which then tightens the band about the drum effectively braking theassembly as above described.

When the forks bearing the box have been elevated sufficiently permitthem to pass above the stack or platform upon which the box is to bedeposited, the operator pushes the truck into position to lower the boxonto the top of the stack. The motor is then stopped, and, if necessary,the operator releases the operating brake, which allows the forks to belowered until the skids attached to the bottom of thebox rest on the topof the stack or platform. The forks then may be withdrawn from betweenthe box and the stack by pulling the truck outwardly and away from thestack.

Whenever necessary during the operation the operator may activate thespring-loaded anti-roll block brake 65 by disengaging floor brake handle77 from its catch 82, permitting the compressed springs 75 and 76 topartially expand downwardly urging block 66 into contact with the floorthus preventing horizontal movement of the truck.

It will be understood that no manual force is applied to the operatingbrake handle during either the lifting or lowering operation to eflectthe braking action as herein described. The manual operation of thebrake handle is only necessary to disengage the brake band from aboutthe drum when the motor is inoperative, such as during the loweringoperation. It is therefore to be noted that the hereinabove describedinterrelation of the brake drum and brake band encircling it, togetherwith the predetermined direction of rotation of the drum by the electricmotor and the urging force supplied by the tension spring to the brakelband, aflfords an automatic brake disengaging mechanism during thepower operation of the lift and an automatic brake engaging mechanismduring the lowering operation. It will also be noted that if for anyreason the operator removes the manual pressure from switch 26, theswitch will reopen, breaking the circuit and stopping the motor, and thebraking action herein described will be effected.

While only a certain preferred embodiment of this invention has beenshown and described by way of illustration, many modifications willoccur to thos skilled in the art and it is, therefore, desired that itbe understood that it is intended in the appended claims to cover allsuch modifications as fall within the true spirit and scope of thisinvention.

What is claimed as new and what it is desired to secure by LettersPatent of the United States is:

1. A fork lift truck comprising a frame, said frame including ahorizontal base having supporting wheels and further including a pair ofspaced, parallel channel bars having front and rear flanges definingoutwardly facing channels, said bars being attached to and extendingupwardly from said base, and four crossmembers, including a topcrossmember, a second crossmember disposed below and adjacent said topcrossmember, a third crossmember below said second crossmember and afourth crossmember below said third crossmember and above said base,said crossmembers connecting said bars in spaced parallel relation, oneof said third and fourth crossmembers lying substantially in the planeof said front flanges and the other lying substantially in the plane ofsaid rear flanges, a fork lift carriage spanning said bars and havingroller means thereon mounted to run on said forward flanges, a spindlerigidly mounted on said one crossmember and extending rearwardlytherefrom, a brake drum having a reel attached thereto and rotatablymounted on said spindle, a brake-lined band having two ends, a pivotfixed to said frame pivotally anchoring one said end externally of andadjacent said drum, said band extending from said pivot and engaginglyencircling in a predetermined direction at least more than one-half ofsaid drum, a tension spring having its ends respectively connected to aportion of said frame and a portion of said second end of said bandurging said band end in said direction into braking engagement with saiddrum, an adjustable attachment element interposed between one end ofsaid spring and its respective connected portion, a pivot member mountedon said frame, a brake handle pivoted at one end to said pivot memberand having an intermediate portion pivotally attached to said secondband end, said band being selectively loosenable and tightenable aboutsaid drum by manual operation of said handle in respective selecteddirections, top idler pulleys mounted to said top crossmember, acarriage pulley mounted on said fork lift carriage, an upper stationarypulley mounted forwardly on said second crossmember adjacent the upperend of said frame, a cable 'having an end at said reel and extendingupwardly therefrom over said top pulleys and downwardly therefrom aroundsaid carriage pulley and upwardly therefrom over said upper pulley anddownwardly therefrom and supportingly connected to said carriage,electric motor means mounted on said other crossmember and extendingrearwardly therefrom and having a drive shaft extending forwardlythrough said other crossmember, said shaft mounting a motor pulleydisposed forwardly of said other crossmember, flexible drive meansconnecting said motor pulley with said drum and reel, a storage batterymounted on said base between said bars, a spring-loaded normally closedlimit switch mounted adjacent the upper end of said frame and engageableby said carriage in an upper limit position, a spring-loaded normallyopen operating switch connected in series with said limit switch, asolenoid relay connected in series with said switches between theterminals of said battery, a connection between said battery and saidmotor through said relay controlled by said relay, said motor beingoperative when energized through said connection to rotatably drive saiddrum and reel in the direction opposite to said predetermined direction,said cable end being wound on said reel in the direction to wind furtherthereon in response to rotation of said reel in said opposite directionand to unwind upon rotation of said reel in said predetermineddirection, whereby rotation of said drum in said opposite directionfrictionally urges said second band end to move against the force ofsaid spring to loosen said band on said drum and rotation of said drumin said predetermined direction tends frictionally to tighten said bandbrakingly about said drum, an anti-roll sping-loaded floor brake blockmounted on said frame, a floor brake handle attached to said block formanually raising and lowering said block, a hook catch mounted on saidframe and engageable by said floor brake handle when said block is in araised position, and a U-shaped tubular handle connecting said channelbars and protruding horizontally rearwards therefrom and passingoutwardly protectingly beyond said drum brake handle.

2. A portable fork lift truck comprising a frame and fork lift carriagemovably engaging said frame, a spindle rigidly mounted on said frame, abrake drum having a reel attached thereto rotatably mounted on saidspindle, a brake-lined band having two ends, a pivot fixed to said framepivotally anchoring one said end externally of and adjacent said drum,said band extending from said pivot and engagingly encircling said drumin a predetermined direction, a tension spring having its endsrespectively connected to a portion of said frame and a portion of saidsecond end of said band urging said band end in said direction intobraking engagement with said drum, an adjustable attachment elementinterposed between one end of said spring and its respective connectedportion, a pivot member mounted on said frame, a brake handle pivoted atone end to said pivot member and having an intermediate portionpivotally attached to said second band end, said band being selectivelyloosenable and tightenable about said drum by manual operation of 27said handle in respective selected directions, a cable supportinglyconnected to said carriage, electric motor means, a flexible driveconnection connecting said motor means with said drum, a source ofelectric power, a control switch, electrical connections connecting saidpower 5 source in circuit with said switch and with said electric motormeans, said control switch being mounted on said frame adjacent saidbrake release handle and biased into position to disconnect said powersource from said motor tion of said reel in said predetermineddirection, whereby rotation of said drum in said opposite directionfrictionally urges said second band end to move against the force ofsaid spring to loosen said band on said drum and rotation of said drumin said predetermined direction tends frictionally to tighten said bandbrakingly about said drum, and a U-shaped handle mounted on said frameand protruding horizontally rearwards therefrom and passing outwardlyprotectingly beyond said means and manually operable to connect saidpower 10 drum brake handle.

source with said motor means, said electrical and flexible driveconnections being oriented to operate said motor means in a direction torotatably drive said drum and reel in the direction opposite to saidpredetermined direction, said cable being wound on said reel in thedirection 15 to wind further thereon in response to rotation of saidreel in said opposite direction and to unwind upon rota- ReferencesCited in the file of this patent UNITED STATES PATENTS 1,781,104 DeLamar Nov. 11, 1930 1,781,700 Payne Nov. 18, 1930 1,875,046 LeTourneauAug. 30, 1932 2,714,434 Peterson Aug. 2, 1955

